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Fix net division to cope with small output sizes.

This commit is contained in:
steve 2001-01-05 03:19:47 +00:00
parent 8bfae1e641
commit 8ee00ec562
1 changed files with 56 additions and 14 deletions
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70
elab_net.cc
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@ -17,7 +17,7 @@
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
*/
#if !defined(WINNT) && !defined(macintosh)
#ident "$Id: elab_net.cc,v 1.55 2000/12/01 02:55:37 steve Exp $"
#ident "$Id: elab_net.cc,v 1.56 2001/01/05 03:19:47 steve Exp $"
#endif
# include "PExpr.h"
@ -534,7 +534,9 @@ NetNet* PEBinary::elaborate_net_cmp_(Design*des, const string&path,
}
/*
* Elaborate a divider gate.
* Elaborate a divider gate. This function create a NetDevide gate
* which has exactly the right sized DataA, DataB and Result ports. If
* the l-value is wider then the result, then pad.
*/
NetNet* PEBinary::elaborate_net_div_(Design*des, const string&path,
unsigned lwidth,
@ -549,36 +551,67 @@ NetNet* PEBinary::elaborate_net_div_(Design*des, const string&path,
NetNet*rsig = right_->elaborate_net(des, path, 0, 0, 0, 0);
if (rsig == 0) return 0;
unsigned rwidth = lsig->pin_count();
if (rsig->pin_count() > rwidth)
rwidth = rsig->pin_count();
// Check the l-value width. If it is unspecified, then use the
// largest operand width as the l-value width. Restrict the
// result width to the width of the largest operand, because
// there is no value is excess divider.
unsigned rwidth = lwidth;
if (rwidth == 0) {
rwidth = lsig->pin_count();
if (rsig->pin_count() > rwidth)
rwidth = rsig->pin_count();
lwidth = rwidth;
}
if ((rwidth > lsig->pin_count()) && (rwidth > rsig->pin_count())) {
rwidth = lsig->pin_count();
if (rsig->pin_count() > rwidth)
rwidth = rsig->pin_count();
}
// Create a device with the calculated dimensions.
NetDivide*div = new NetDivide(des->local_symbol(path), rwidth,
lsig->pin_count(),
rsig->pin_count());
des->add_node(div);
// Connect the left and right inputs of the divider to the
// nets that are the left and right expressions.
for (unsigned idx = 0 ; idx < lsig->pin_count() ; idx += 1)
connect(div->pin_DataA(idx), lsig->pin(idx));
for (unsigned idx = 0 ; idx < rsig->pin_count() ; idx += 1)
connect(div->pin_DataB(idx), rsig->pin(idx));
if (lwidth == 0) lwidth = rwidth;
// Make an output signal that is the width of the l-value.
// Due to above calculation of rwidth, we know that the result
// will be no more then the l-value, so it is safe to connect
// all the result pins to the osig.
NetNet*osig = new NetNet(scope, des->local_symbol(path),
NetNet::IMPLICIT, lwidth);
osig->local_flag(true);
unsigned cnt = osig->pin_count();
if (cnt > rwidth) cnt = rwidth;
for (unsigned idx = 0 ; idx < cnt ; idx += 1)
for (unsigned idx = 0 ; idx < rwidth ; idx += 1)
connect(div->pin_Result(idx), osig->pin(idx));
/* If the lvalue is larger then the result, then pad the
output with constant 0. */
if (cnt < osig->pin_count()) {
// If the lvalue is larger then the result, then pad the
// output with constant 0. This can happen for example in
// cases like this:
// wire [3;0] a, b;
// wire [7:0] r = a / b;
if (rwidth < osig->pin_count()) {
NetConst*tmp = new NetConst(des->local_symbol(path), verinum::V0);
des->add_node(tmp);
for (unsigned idx = cnt ; idx < osig->pin_count() ; idx += 1)
for (unsigned idx = rwidth ; idx < osig->pin_count() ; idx += 1)
connect(osig->pin(idx), tmp->pin(0));
}
@ -1450,8 +1483,14 @@ NetNet* PENumber::elaborate_net(Design*des, const string&path,
return net;
}
#if 0
/* This warning is trying to catch the cases where an unsized
integer in a netlist causes the netlist to explode in width
even when it need not. This proved to be spurious and
caused lots of false alarms, so it is commented out. */
cerr << get_line() << ": warning: Number with indefinite size "
<< "in self-determined context." << endl;
#endif
/* None of the above tight constraints are present, so make a
plausible choice for the width. Try to reduce the width as
@ -1758,6 +1797,9 @@ NetNet* PEUnary::elaborate_net(Design*des, const string&path,
/*
* $Log: elab_net.cc,v $
* Revision 1.56 2001/01/05 03:19:47 steve
* Fix net division to cope with small output sizes.
*
* Revision 1.55 2000/12/01 02:55:37 steve
* Detect part select errors on l-values.
*